U.S. patent number 5,027,114 [Application Number 07/249,173] was granted by the patent office on 1991-06-25 for ground guidance system for airplanes.
Invention is credited to Koichi Futsuhara, Kiroshi Kawashima, Fumio Wada.
United States Patent |
5,027,114 |
Kawashima , et al. |
June 25, 1991 |
**Please see images for:
( Certificate of Correction ) ** |
Ground guidance system for airplanes
Abstract
A ground guidance system for airplanes in which loop coils of a
predetermined shape are continuously buried in a specific section
of a taxiway for airplanes, an airplane is continuously detected
based on changes of self-inductances of the loop coils with
movement of the airplane while discriminating airplanes from other
objects and admission or inhibition of advance in the specific
section to a subsequent airplane according to the presence or
absence of the airplane in the specific section and which has a
fail-safe structure not generating an output at the time of a
system or circuit failure or accident.
Inventors: |
Kawashima; Kiroshi (Mitaka-shi,
Tokyo 181, JP), Futsuhara; Koichi (Omiya-shi, Saitama
330, JP), Wada; Fumio (Urawa-shi, Saitama 336,
JP) |
Family
ID: |
13902699 |
Appl.
No.: |
07/249,173 |
Filed: |
August 15, 1988 |
PCT
Filed: |
June 09, 1987 |
PCT No.: |
PCT/JP87/00367 |
371
Date: |
August 15, 1988 |
102(e)
Date: |
August 15, 1988 |
PCT
Pub. No.: |
WO88/09982 |
PCT
Pub. Date: |
December 15, 1988 |
Current U.S.
Class: |
340/941;
340/958 |
Current CPC
Class: |
G08G
5/0026 (20130101); G08G 5/0082 (20130101); G08G
5/065 (20130101) |
Current International
Class: |
G08G
5/06 (20060101); G08G 5/00 (20060101); G08G
001/01 () |
Field of
Search: |
;340/933,941,945,958,961,989 ;342/36,29,63 ;364/424.01,439,441,460
;244/114R ;73/178R ;180/168 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"At the Crossroads in Air Traffic Control", Friedlander, IEEE
Spectrum Jul. 1970, pp. 69, 76, 77..
|
Primary Examiner: Orsino; Joseph A.
Assistant Examiner: Swarthout; Brent A.
Attorney, Agent or Firm: Lowe, Price, Leblanc &
Becker
Claims
What is claimed is:
1. A ground guidance system for airplanes in an airplane taxiway
divided in a plurality of control sections, which comprises a
plurality of loop coils in which the side parallel to the direction
of advance of airplanes has a length larger than the length of an
automobile but smaller than the length of an airplane and which are
arranged in the direction of advance of airplanes in the control
sections at intervals smaller than the length of an airplane, a
plurality of airplane-detecting means arranged for the respective
loop coils to generate detection outputs indicating the presence or
absence of an airplane based on changes of self-inductances of the
corresponding loop coils, display means for displaying admission of
advance or inhibition of advance in the control sections for an
airplane, and control means of controlling said display means based
on detection outputs of a plurality of said airplane-detecting
means,
wherein the airplane-detecting means is constructed so that a
high-level output is generated at the time of non-detection of an
airplane and a low-level output is generated at the time of
detection of an airplane, and at the time of a failure, the output
errs to a voltage corresponding to said low-level output at the
time of detection of an airplane,
said airplane-detecting means comprising a high-frequency signal
generator, a bridge circuit including three resistors and a
resonance circuit consisting of one said loop coil and a capacitor,
which becomes substantially resonant with the output frequency of
the high-frequency signal generator, an alternating current
amplifier for amplifying the output of the bridge circuit, a
wave-detecting circuit for detecting an envelope of the amplified
output of the alternating current amplifier, a window comparator
having such a window characteristic that the output signal of the
wave-detecting circuit is received as the input signal, the output
level of the wave-detecting circuit obtained when an airplane is
not present in the taxiway is within the window and the output
level of the wave-detecting circuit obtained when an airplane is
present and the self-inductance of the loop coil is changed is
outside the window, and generating an output when an input signal
of the level within the window is put in, and a voltage multiplying
rectifying circuit for rectifying the output of the window
comparator.
2. A ground guidance system for airplanes according to claim 1,
wherein the window comparator is constructed by connecting first
and second input terminals of a logical product-computing
oscillating means which generates an oscillating output when input
signals of a predetermined high level higher than the level of a
power source voltage are simultaneously applied to the first and
second input terminals.
3. A ground guidance system for airplanes according to claim 2,
wherein the logical product-computing oscillating means comprises a
first transistor having a collector connected o the first input
terminal of the logical product-computing oscillating means through
a first collector resistor and an emitter connected to an input
terminal of the power source, a second transistor having an emitter
connected to the input terminal of the power source and a collector
connected to a reference voltage source through second and third
collector resistors connected in series, in which the collector
voltage of the first transistor divided by a potential-dividing
resistor formed by said second and third collector resistors
arranged between the collector and the reference voltage source is
put into a base of said second transistor, and a third transistor
having a collector connected to the second input terminal of the
logical product-computing oscillating means through fourth and
fifth collector resistors and an emitter connected to said
reference voltage source, in which the collector voltage of the
second transistor divided by the second and third collector
resistors is put into the base, and the input signal voltage
applied to the second input terminal divided by the fourth and
fifth collector resistors is put into the base of the first
transistor through a resistor and the collector of the third
transistor is connected to the output terminal of the logical
product-computing oscillating means,.
4. A ground guidance system for airplanes in an airplane taxiway
divided in a plurality of control sections, which comprises a
plurality of loop coils in which the side parallel to the direction
of advance of airplanes has a length larger than the length of an
automobile but smaller than the length of an airplane and which are
arranged in the direction of advance of airplanes in the control
sections at intervals smaller than the length of an airplane, a
plurality of airplane-detecting means arranged for the respective
loop coils to generate detection outputs indicting the presence or
absence of an airplane based on changes of self-inductances of the
corresponding loop coils, display means for displaying admission of
advance or inhibition of advance in the control sections for an
airplane, and control means for controlling said display means
based on detection outputs of a plurality of said
airplane-detecting means,
wherein the control means comprises a direction- and
object-discriminating circuit for detecting the advance direction
of an airplane and discriminating an airplane from an automobile
based on an output from the airplane-detecting means corresponding
to the loop coil within the control section in which an airplane
advances and a display-instructing circuit for generating a signal
for instructing admission of advance of an airplane or a signal for
inhibition of advance of an airplane in the control section in the
rear of the control section in which an airplane advances, based on
the output of the airplane-detecting means corresponding to the
loop coil of said rear control section and the output of the
direction- and object-discriminating circuit.
5. A ground guidance system for airplanes according to claim 4,
wherein the direction- and object-discriminating circuit generates
a direction detection output of a high voltage only when an
airplane moves from the inlet side to the exit side in the control
section.
6. A ground guidance system for airplanes according to claim 5,
wherein the direction- and object-discriminating circuit comprises
a first AND gate connected to adjacent loop coils, in which the
output of the airplane-detecting means is put through an inverter,
first self-retention means for feeding back the rectified output of
the first AND gate through a resistor to the input terminal of the
first AND gate in which the output of the airplane-detecting means
connected to the loop coil located on the inlet side of the control
section is put and self-retaining the output of the first AND gate,
a second AND gate in which the output of the first AND gate and the
output of the airplane-detecting means connected to the loop coil
on the inlet side of the control section are put, a third AND gate
in which the rectified output of the second AND gate and the output
of the airplane-detecting means connected to the loop coil located
on the exit side of the control section are put, and a second
self-retention means for feeding back the rectified output of the
third AND gate through a resistor to the input terminal of the
third AND gate in which the output of the second AND gate is put
and self-retaining the output of the third AND gate.
7. A ground guidance system for airplanes according to claim 6,
wherein the first, second and third AND gates constitute a logical
product-computing oscillating means which generates oscillating
outputs from the output terminals when input signals of a
predetermined level higher than a power source voltage are applied
to the first and second input terminals.
8. A ground guidance system for airplanes according to claim 6,
wherein the display-instructing circuit comprises an
advance-admitting signal generating means for generating an
advance-admitting signal of a high voltage when a direction-setting
signal fed from a manual operating device operated by an air
traffic controller is in agreement with the output signal of the
direction- and object-discriminating circuit and a
running-admitting signal is supplied from the manual operating
device, an advance-inhibiting signal-generating means for
generating an advance-inhibiting signal of a low level for
inhibiting advance of an airplane in the control section in the
rear of the control section in which an airplane advances when an
airplane-detecting signal is generated from at least one of the
airplane-detecting means connected to the loop coils in said rear
control sections and emitting an advance-inhibiting
display-instructing signal of a low level to said display means,
and an advance-admitting instructing means for emitting an
advance-admitting display-instructing signal of a high level to
said display means when the advance-admitting signal-generating
means generates the advance-admitting signal and the
advance-inhibiting signal-generating means does not generate the
advance-inhibiting signal.
9. A ground guidance system for airplanes according to claim 8,
wherein the advance-admitting signal-generating means comprises a
fourth AND gate in which the output of the direction- and
object-discriminating circuit and the direction-setting signal of
the manual operating device are put and a fifth AND gate in which
the rectified output of the fourth AND gate and the
running-admitting signal of the manual operating device are
put.
10. A ground guidance system for airplanes according to claim 9,
wherein the fourth and fifth AND gates constitute a logical
product-computing means generating oscillating outputs from the
output terminals when input signals of a predetermined level higher
than the level of a power source voltage are applied to the first
and second input terminals.
11. A ground guidance system for airplanes according to claim 9,
wherein the advance-inhibiting signal-generating means comprises a
sixth AND gate receiving the outputs of the airplane-detecting
means as inputs.
12. A ground guidance system for airplanes according to claim 11,
wherein the sixth AND gate constitutes the logical
product-computing oscillating means generating an oscillating
output when input signals of a predetermined level higher than the
level of power source voltage are applied to the first and second
input terminals.
13. A ground guidance system for airplanes according to claim 12,
wherein the advance-admitting instructing means comprises a seventh
AND gate receiving the outputs of the advance-admitting
signal-generating means and the advance-inhibiting
signal-generating means as inputs.
14. A ground guidance system for airplanes according to claim 13,
wherein the seventh AND gate constitutes a logical
product-computing oscillating means generating an oscillating
output from the output terminal when input signals of a
predetermined level higher than the level of a power source voltage
are applied to the first and second input terminals.
15. A ground guidance system for airplanes according to claim 8,
wherein the manual operating device comprises a changeover switch
for effecting changeover between automatic control and manual
control of the display means, a direction-setting switch for
generating the direction-setting signal for setting the advance
direction of an airplane in the taxiway, a manual running-admitting
instructing switch for optionally generating the running-admitting
signal to the control section by an air traffic controller when the
changeover switch is on the manual control side, and a
running-inhibiting instructing changeover switch for cancelling the
instruction signals of the changeover switch, the directionsetting
switch and the manual running-admitting instructing switch and
generating a running-inhibiting instructing signal.
16. A ground guidance system for airplanes according to claim 4,
wherein the display-instructing circuit comprises an
advance-admitting signal-generating means for generating an
advance-admitting signal of a high level when a direction-setting
signal supplied from a manual operating device operated by an air
traffic controller is in agreement with the output signal from the
direction- and object-discrimination circuit and a non-detection
signal is generated from the airplane-detecting means connected to
one said loop coil arranged in a predetermined area of the control
section in the rear of the control section in which the
running-admitting signal is put from the manual operating device,
said ground guidance system further comprising an
advance-inhibiting signal-generating means emitting an airplane
advance-inhibiting signal of a low level to the control section in
the rear of the control section when an airplane detection signal
is generated from at least one of the airplane-detecting means
connected to loop coils arranged in said predetermined area in the
rear of said control section and emitting a signal of a low level
for instructing display of inhibition of advance to said display
means, and an advance-admitting instructing means for emitting a
signal of a high level for instructing display of admission of
advance only when the advance-admitting signal-generating means
generates the advance-admitting signal and the advance-inhibiting
signal-generating means generates the advance-inhibiting
signal.
17. A ground guidance system for airplanes according to claim 8,
wherein the display means comprises an advance-admitting signal
lamp having a constant current source as a power source and
displaying admission of advance to an airplane, an
advance-admitting lamp controlling switch means for performing
on-off control of the advance-admitting signal lamp based on
instructions from an advance-admitting instructing means, an
advance-inhibiting signal lamp having a constant current source as
a power source and displaying inhibition of advance in a front
control section to an airplane, and an advance-inhibiting
lamp-controlling switch means for performing on-off control of the
advance-inhibiting signal lamp based on instructions from the
advance-inhibiting signal-generating means.
18. A ground guidance system for airplanes according to claim 17,
wherein the advance-admitting lamp-controlling switch means
comprises said constant current power source, said
advance-admitting signal lamp connected to said constant current
power source, a switch element connected in parallel to the
advance-admitting signal lamp to control supply of an electric
current to the advance-admitting signal lamp according to the input
signal, a current-detecting means for detecting the electric
current supplied to the advance-admitting signal lamp, which is
controlled by said switch element, a watch means for determining
normal and abnormal states of the advance-admitting
lamp-controlling switch means based on the input signal and the
detection output of the current-detecting means, and a current
cut-off means for cutting the connection between the constant
current power source and the advance-admitting signal lamp when
said watch means detects the abnormal state.
19. A ground guidance system for airplanes according to claim 17,
wherein the advance-inhibiting lamp-controlling switch means
comprises said constant current power source, said
advance-inhibiting signal lamp connected to said constant current
power source and a switch element connected in parallel to said
advance-inhibiting signal lamp, which is turned off when an input
signal of a low level including an output at the time of a circuit
failure is supplied and is turned on when an input signal of a high
level not including an output at the time of a circuit failure is
supplied.
20. A ground guidance system for airplanes according to claim 4,
wherein the display-instructing means comprises a plurality of AND
gates having, as a reset signal, a logical sum output of adjacent
airplane-detecting means generating airplane-detecting outputs in
sequence with the movement of an airplane and, as a present signal,
the rising component of the output signal of the airplane-detecting
means located, in the airplane advance direction, between one of
said adjacent airplane-detecting means and an advance-admitting
signal to a subsequent airplane in the airplane-advancing control
section, which is generated in the control section in front of the
airplane-advancing control section a plurality of self-retention
circuits for feeding back the rectified outputs of the respective
AND gates to preset input terminals of the AND gates and
self-retaining the outputs of respective AND gates, and an
advance-inhibiting signal-generating redundant control means having
other AND gates which receive the outputs of said plurality of AND
gates for generating an advance-inhibiting signal of a low level
including a failure output when any one of the AND gates does not
generate an output.
21. In a ground guidance system for airplanes having an airplane
taxiway divided into a plurality of control sections, each control
section having a plurality of loop coils for detecting vehicles on
said taxiway, the improvement comprising:
said loop coils having a dimension parallel to the direction of
advance of airplanes which is smaller than the length of an
airplane to be detected and said loop coils being arranged in the
direction of advance of airplanes on said taxiway in the control
sections at intervals smaller than the length of an airplane, said
length of said dimension of said loop coils in said direction of
advance of airplanes being larger than the length of an automobile;
each said loop coil being directly connected to airplane-detecting
means to generate detection outputs indicating the presence or
absence of an airplane in the vicinity of each said loop coil,
wherein said airplane-detecting means comprises a high-frequency
signal generator, a bridge circuit including three resistors and a
resonance circuit consisting of one said loop coil and a capacitor,
which becomes substantially resonant with the output frequency of
the high-frequency signal generator, an alternating current
amplifier for amplifying the output of the bridge circuit, a
wave-detecting circuit for detecting an envelope of the amplified
output of the alternating current amplifier, a window comparator
means responsive to said wave-detecting circuit having a window
characteristic such that the output level of the wave-detecting
circuit obtained when an airplane is not present in the taxiway is
within the window and the output level of the wave-detecting
circuit obtained when an airplane is present and the
self-inductance of the loop coil is changed is outside the window,
for generating an output when an input signal of the level within
the window is put in, and a voltage multiplying rectifying circuit
for rectifying the output of the window comparator.
22. A ground guidance system for airplanes according to claim 4,
wherein the display-instructing circuit comprises an
advance-admitting signal generating means for generating an
advance-admitting signal of a high voltage when a direction-setting
signal fed from a manual operating device operated by an air
traffic controller is in agreement with the output signal of the
direction- and object-discriminating circuit and a
running-admitting signal is supplied from the manual operating
device, an advance-inhibiting signal-generating means for
generating an advance-inhibiting signal of a low level for
inhibiting advance of an airplane in the control section in the
rear of the control section in which an airplane advances when an
airplane-detecting signal is generated from at least one of the
airplane-detecting means connected to the loop coils in said rear
control sections and emitting an advance-inhibiting
display-instructing signal of a low level to said display means,
and an advance-admitting instructing means for emitting an
advance-admitting display-instructing signal of a high level to
said display means when the advance-admitting signal-generating
means generates the advance-admitting signal and the
advance-inhibiting signal-generating means does not generate the
advance-inhibiting signal.
23. A ground guidance system for airplanes according to claim 22,
wherein the advance-admitting signal-generating means comprises a
first AND gate in which the output of the direction-and
object-discriminating circuit and the direction-setting signal of
the manual operating device are put and a second AND gate in which
the rectified output of the first AND gate and the
running-admitting signal of the manual operating device are
put.
24. A ground guidance system for airplanes according to claim 23,
wherein the first and second AND gates constitute a logical
product-computing means generating oscillating outputs from the
output terminals when input signals of a predetermined level higher
than the level of a power source voltage are applied to the first
and second input terminals.
25. A ground guidance system for airplanes according to claim 23,
wherein the advance-inhibiting signal-generating means comprises a
third AND gate receiving the outputs of the airplane-detecting
means as inputs.
26. A ground guidance system for airplanes according to claim 25,
wherein the third AND gate constitutes the logical
product-computing oscillating means generating an oscillating
output when input signals of a predetermined level higher than the
level of a power source voltage are applied to the first and second
input terminals.
27. A ground guidance system for airplanes according to claim 26,
wherein the advance-admitting instructing means comprises a fourth
AND gate receiving the outputs of the advance-admitting
signal-generating means and the advance-inhibiting
signal-generating means as inputs.
28. A ground guidance system for airplanes according to claim 27,
wherein the fourth AND gate constitutes a logical product-computing
oscillating means generating an oscillating output from the output
terminal when input signals of a predetermined level higher than
the level of a power source voltage are applied to the first and
second input terminals.
29. A ground guidance system having an airplane taxiway divided
into a plurality of control sections, each control section having a
plurality of loop coils for detecting vehicles on said taxiway,
wherein
said loop coils have a dimension parallel to the direction of
advance of airplanes which is smaller than the length of an
airplane to be detected and said loop coils are arranged in the
direction of advance of airplanes on said taxiway in the control
sections at intervals smaller than the length of an airplane, said
length of said dimension of said loop coils in said direction of
advance of airplanes being larger than the length of an automobile;
each said loop coil being directly connected to vehicle-detecting
means to generate detection outputs indicating the presence or
absence of an airplane in the vicinity of each said loop coil,
wherein said vehicle-detecting means comprises a high-frequency
signal generator, a bridge circuit including three resistors and a
resonance circuit consisting of one said loop coil and a capacitor,
which becomes substantially resonant with the output frequency of
the high-frequency signal generator, an alternating current
amplifier for amplifying the output of the bridge circuit, a
wave-detecting circuit for detecting an envelope of the amplified
output of the alternating current amplifier, a window comparator
means responsive to said wave-detecting circuit having a window
characteristic such that the output level of the wave-detecting
circuit obtained when an airplane is not present in the taxiway is
within the window and the output level of the wave-detecting
circuit obtained when an airplane is present and the
self-inductance of the loop coil is changed is outside the window,
for generating an output when an input signal of the level within
the window is put in, and a voltage multiplying rectifying circuit
for rectifying the output of the window comparator.
30. A ground guidance system according to claim 29, further
including control means including a direction- and
object-discriminating circuit for detecting the advance direction
of an airplane and means for discriminating an airplane from an
automobile based on an output from the vehicle-detecting means
corresponding to the loop coil within the control section in which
an airplane advances and a display-instructing circuit for
generating a signal for instructing admission of advance of an
airplane or a signal for inhibition of advance of an airplane in
the control section in the rear of the control section in which an
airplane advances, based on the output of the vehicle-detecting
means corresponding to the loop coil of said rear control section
and the output of the direction- and object-discriminating
circuit.
31. A ground guidance system for airplanes according to claim 30,
wherein said display-instructing circuit comprises an
advance-admitting signal generating means for generating an
advance-admitting signal of a high voltage when a direction-setting
signal fed from a manual operating device operated by an air
traffic controller is in agreement with the output signal of the
direction- and object-discriminating circuit and a
running-admitting signal is supplied from the manual operating
device, an advance-inhibiting signal-generating means for
generating an advance-inhibiting signal of a low level for
inhibiting advance of an airplane in the control section in the
rear of the control section in which an airplane advances when a
vehicle-detecting signal is generated from at least one of the
vehicle-detecting means connected to the loop coils in said rear
control sections and emitting an advance-inhibiting
display-instructing signal of a low level to said display means,
and an advance-admitting instructing means for emitting an
advance-admitting display-instructing signal of a high level to
said display means when the advance-admitting signal-generating
means generates the advance-admitting signal and the
advance-inhibiting signal-generating means does not generate the
advance-inhibiting signal.
32. A ground guidance system according to claim 31, wherein the
manual operating device comprises a changeover switch for effecting
changeover between automatic control and manual control of the
display means, a direction-setting switch for generating the
direction-setting signal for setting the advance direction of an
airplane in the taxiway, a manual running-admitting instructing
switch for optionally generating the running-admitting signal to
the control section by an air traffic controller when the
changeover switch is on the manual control side, and a
running-inhibiting instructing changeover switch for cancelling the
instruction signals of the changeover switch, the direction-setting
switch and the manual running-admitting instructing switch and
generating a running-inhibiting instructing signal.
33. A ground guidance system according to claim 30, wherein the
display-instructing circuit comprises an advance-admitting
signal-generating means for generating an advance-admitting signal
of a high level when a direction-setting signal supplied from a
manual operating device operated by an air traffic controller is in
agreement with the output signal from the direction- and
object-discrimination circuit and a non-detection signal is
generated from the airplane-detecting means connected to one said
loop coil arranged in a predetermined area of the control section
in the rear of the control section in which the running-admitting
signal is put from the manual operating device, said ground
guidance system further comprising an advance-inhibiting
signal-generating means emitting an airplane advance-inhibiting
signal of a low level to the control section in the rear of the
control section when an airplane detection signal is generated from
at least one of the vehicle-detecting means connected to the loop
coils arranged in said predetermined area in the rear of said
control section and emitting a signal of a low level for
instructing display of inhibition of advance to said display means,
and an advance-admitting instructing means for emitting a signal of
a high level for instructing display of admission of advance only
when the advance-admitting signal-generating means generates the
advance-admitting signal and the advance-inhibiting
signal-generating means generates the advance-inhibiting
signal.
34. A ground guidance system according to claim 31, wherein the
display means comprises an advance-admitting signal lamp having a
constant current source as a power source and displaying admission
of advance to an airplane, an advance-admitting lamp controlling
switch means for performing on-off control of the advance-admitting
signal lamp based on instructions from an advance-admitting
instructing means, an advance-inhibiting signal lamp having a
constant current source as a power source and displaying inhibition
of advance in the front control section to an airplane, and an
advance-inhibiting lamp-controlling switch means for performing
on-off control of the advance-inhibiting signal lamp based on
instructions from the advance-inhibiting signal-generating
means.
35. A ground guidance system according to claim 29, wherein the
control means comprises a plurality of direction- and
object-discriminating circuits receiving an input signals the
output signals of adjacent vehicle-detecting means in the control
sections for generating airplane detection outputs in sequence with
movement of an airplane and detecting the direction of advance of
the airplane, a plurality of AND gates receiving the outputs of a
plurality of the direction- and object-discriminating circuits as
one input signal and receiving as another input signal wired OR
outputs of vehicle-detecting means in to the rear of said control
section, in the range from the last vehicle-detecting means to the
vehicle-detecting means located just ahead of the vehicle-detecting
means located on the opposite side to the airplane advance
direction, the signal of which is put in the direction- and
object-discriminating circuits, a wired OR circuit for computing
the logical sum of the outputs of said AND gates, and a direction-
and object-discriminating signal-generating redundant control means
for converting the output of the wired OR circuit to a direction-
and object-discriminating signal for forming an advance-admitting
signal to the control sections to the rear of said control
section.
36. A ground guidance system for airplanes according to claim 30,
wherein the display-instructing means comprises a plurality of AND
gates having, as a reset signal, a logical sum output of adjacent
vehicle-detecting means generating vehicle-detecting outputs in
sequence with the movement of an airplane and, as a present signal,
the rising component of the output signal of the vehicle-detecting
means located ,in the airplane advance direction, between one of
said adjacent vehicle-detecting means and an advance-admitting
signal to a subsequent airplane in the airplane-advancing control
section, which is generated in the control section in front of the
airplane-advancing control section, a plurality of self-retention
circuits for feeding back the rectified outputs of the respective
AND gates to preset input terminals of the AND gates and
self-retaining the outputs of respective AND gates and an
advance-inhibiting signal-generating redundant control means having
other AND gates which receive the outputs of said plurality of AND
gates for generating an advance-inhibiting signal of a low level
including a failure output when any one of the AND gates does not
generate an output.
Description
DESCRIPTION
This application corresponds to application PCT/JP 87/00367, filed
June 9,1987.
TECHNICAL FIELD
The present invention relates to a ground guidance system for
airplanes, which safely guides and controls an airplane advancing
into a taxiway or present in the taxiway.
BACKGROUND ART
As means for preventing a contact or collision between airplanes on
the ground, there has been proposed an airplane ground guidance
system in which a taxiway is divided into several continuous
sections having a certain length, for example, about 100 m, an
airplane-detecting apparatus is arranged in each control section
and a subsequent airplane is prevented from advancing in a control
section in which an airplane is already present (see Report of
Investigation of Airplane Guidance System in Taxiways and Aprons of
New Tokyo International Air Port, 1969-1975, by Aviation Promotion
Foundation).
According to this system, one rectangular coil loop in which the
length of the side parallel to the direction of advance of an
airplane is much shorter than the airplane length, for example, 3
to 5 m, is arranged on each of inlet and exit sides of each control
section so that the distance between the loop coils on inlet and
exit sides is about 90 to about 100 m, the change of the
self-inductance caused on passage of an airplane through the loop
coil on the inlet side is detected by a sensor and a memory is
brought into the set state by a signal of the sensor, whereby an
advance-inhibiting lamp indicating the presence of an airplane in
the control section is lighted to inhibit a subsequent airplane
from advancing in this control section.
When the above-mentioned airplane which has advanced into the
control section passes through the loop coil on the exit side, the
memory in the set state is reset by an output signal from a
corresponding sensor and an advance-admitting lamp indicating the
absence of an airplane is lighted, whereby a subsequent airplane is
allowed to advance into the control section.
Namely, occurrence of a contact or collision accident on the ground
is prevented by allowing only one airplane to be present in one
control section
Not only airplanes but also various automobiles such as
passenger-transporting buses and maintenance vehicles run on the
taxiway, and the change of the self-inductance is caused in the
loop coil by passage of such a vehicle and a detection output is
generated in the airplane-detecting apparatus. Moreover, these
automobiles do not always run just on the taxiway but they often
cross the taxiway, and there is a good possibility that automobiles
pass only on one loop coil on the inlet or exit side.
In this case, in the above-mentioned guidance system in which the
memory is set and reset, for example, when an automobile passes on
the loop coil on the inlet side even into the absence of an
airplane in the control section, the memory is set, and if the
memory is not reset, a subsequent airplane is not allowed to
advance in the control section. On the other hand, if an automobile
passes on the loop coil on the exit side, since the memory into the
set state is reset, the advance-admitting lamp is lighted even in
the presence of an airplane in the control section, there is a risk
of advance of subsequent airplane in the control section.
Furthermore, in this control system, the control is established
even in case of an automobile which is much smaller than an
airplane, and it happens that the control section is occupied by
one automobile and the operation efficiency of the taxiway si
drastically reduced.
It is a primary object of the present invention to obviate the
disadvantages of the above-mentioned system and provide an airplane
guidance system in which an airplane is continuously detected in
control sections of a taxiway for airplanes, an airplane is
discriminated from an automobile by generating different detection
patterns and guidance of an airplane is performed safely at a high
efficiency.
DISCLOSURE OF THE INVENTION
In accordance with the present invention, the above-mentioned
object can be attained by a ground guidance system for airplanes in
an airplane taxiway divided in a plurality of control sections,
which comprises a plurality of loop coils in which the side
parallel to the direction of advance of airplanes has a length
larger than the length of an automobile but smaller than the length
of an airplane and which are arranged in the direction of advance
of airplanes in the control sections at intervals smaller than the
length of an airplane, a plurality of airplane-detecting means
arranged for the respective loop coils to generate detection
outputs indicating the presence or absence of an airplane based on
changes of self-inductances of the corresponding loop coils,
display means for displaying admission of advance or inhibition of
advance in the control sections for an airplane, and control means
for controlling said display means based on detection outputs of a
plurality of said airplane-detecting means. In this control system,
airplane detection signals of two sensors corresponding to adjacent
loop coils are always put out in the partially overlapped state and
an airplane can be continuously detected. On the other hand, in
case of an automobile, detection signals of both the sensors are
not overlapped and they become discontinuous, and the detection
pattern of an automobile becomes different from the detection
pattern of an airplane and they can be discriminated from each
other. Therefore, guidance control of an airplane is not influenced
by passage of an automobile. Moreover, it does not happen that one
control section is occupied by one automobile. Therefore, a system
which can guide an airplane safely at high efficiency can be
provided.
Furthermore, in the present invention, a memory in which a
fail-safe structure cannot be realized need not be used and signal
processing is performed in the guidance system by using logical
computing means having such a fail-safe structure that no output is
generated at the time of a failure, and such a correspondence
relation is established between the presence or absence of an
airplane in the control section and the output state of the
airplane-detecting means that logical value 1 (high voltage) is
produced in case of the absence of an airplane and logical value 0
(low voltage including zero) is produced in case of the presence of
an airplane. A power source for a driving circuit of an
advance-inhibiting signal lamp displaying inhibition of advance in
the forward control section is constructed by a constant current
power source so that the advance-inhibiting signal lamp is lighted
at the time of detection of an airplane or occurrence of a failure,
whereby a fail-safe structure can be imparted to the guidance
system.
Moreover, the system of the present invention is constructed so
that only when the direction indicated by an air traffic controller
is in agreement with the advance direction of an airplane, an
advance-admitting signal can be generated to set the moving
direction of the airplane and bidirectional guidance becomes
possible.
Still further, the system of the present invention is constructed
so that the guidance control for airplanes can be changed over
between manual control and automatic control and if an accident
occurs on a taxiway, the movement of an airplane in a specific
region of the taxiway or the entire taxiway is inhibited or the
airplane is moved according to instructions of an air traffic
controller, whereby the accident can be appropriately coped
with.
In order to cope with the case where even if the rear end portion
of an airplane is left in a loop coil, since the rear end portion
is located at a high position and the change of the self-inductance
of the loop coil is small, the airplane-detecting means generates a
non-detection output, the system of the present invention is
constructed so that on condition that no airplane is present in a
predetermined loop coil in the rear of the loop coil where an
airplane is now present an advance admission signal is produced for
a subsequent airplane, whereby the safety is further increased.
Still in addition, the system of the present invention is
constructed so that even if one of a plurality of loop coils or
airplane-detecting means arranged in one control section gets out
of order, guidance of an airplane is maintained by the remaining
normal loop coils or airplane-detecting means. In this case, the
admission signal lamp should not be lighted before the lighting
point at the time when all of the loop coils and airplane-detecting
means are normal and the advance-inhibiting signal lamp should not
be lighted after the lighting point at the time when all of the
loop coils and airplane-detecting means are normal.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating one embodiment of the ground
guidance system for airplanes according to the present
invention.
FIG. 2 is a circuit diagram of a sensor in the embodiment shown in
FIG. 1.
FIG. 3 is a time chart illustrating the operation of the sensor
shown in FIG. 2.
FIG. 4(A) and 4(B) are diagrams illustrating changes of the
self-inductance observed when an airplane and an automobile advance
in a loop coil, respectively.
FIG. 5 is a circuit diagram of a logical product computing
oscillator as a constituent element of a window comparator of the
sensor shown in FIG. 2.
FIG. 6 is a circuit diagram of a rectifying circuit in the sensor
shown in FIG. 2.
FIG. 7 is a circuit diagram of a direction- and
object-discriminating circuit in the embodiment shown in FIG.
1.
FIG. 8 is a time chart illustrating the operation of the direction
and object-discriminating circuit shown in FIG. 7.
FIG. 9 is a diagram illustrating the structure of a
display-instructing circuit in the embodiment shown in FIG. 1.
FIG. 10 is a diagram illustrating a switch circuit for an admission
signal lamp in the embodiment shown in FIG. 1.
FIG. 11 is a circuit diagram illustrating the structure of a main
part of another embodiment of the admission signal lamp.
FIG. 12 is a diagram illustrating a switch circuit for an
inhibition signal lamp.
FIG. 13 is a circuit diagram illustrating another embodiment of the
display-instructing circuit.
FIGS. 14(A), 14(B) and 14(C) are diagrams illustrating the control
system for different airplane running patterns at the crossing
point of taxiways in the embodiment shown in FIG. 1.
FIG. 15 is a diagram illustrating a direction- and
object-discriminating signal-generating circuit having a redundant
function.
FIG. 16 is a diagram illustrating an inhibition signal-generating
circuit having a redundant function.
FIG. 17 is a time chart illustrating the operation of the
inhibition signal-generating circuit shown in FIG. 16.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will now be described in detail with
reference to the accompanying drawings.
Referring to FIG. 1, a plurality of loop coils .lambda. i (i=1, 2,
..) are continuously buried in a taxiway 1 at intervals shorter
than the length of an airplane along the direction of advance cf an
airplane (the direction indicated by an arrow in FIG. 1) in the
taxiway 1 for airplanes.
The loop coil 1 has such a rectangular shape that the length of the
side a parallel to the direction of advance of an airplane in the
taxiway 1 is smaller than the length of an airplane but larger than
the length of an automobile, for example, the length of the side, a
is 30 m and the side b orthogonal to the side a is 30 m. The
taxiway 1 is divided into a plurality of control sections D having
a length of, for example, 100 m, and, for example, three loop coils
.lambda. i are arranged in each control section D.
In the loop coil .lambda. i, the self-inductance is changed by
passage through an airplane, and this change is detected by a
sensor Si (i=1, 2, ...) corresponding to the loop coil .lambda. i
to put out a signal of detection of the absence or presence of an
airplane to a signal processing unit 2 as the control means.
The signal processing unit 2 comprises a direction- and
object-discriminating circuit 3, described hereinafter, for
detecting the direction of advance of an airplane and
discriminating an automobile and a display-instruction circuit 4
and controls signal lamp switch circuits 6 and 7 as signal lamp
switch control means for turning on and off a green signal lamp G
displaying admission of advance of an airplane into the control
section D and a red signal lamp R displaying inhibition of advance
based on a detection signal from the sensor Si and an instruction
signal from a manual operation device 5 operated by an air traffic
controller. If an airplane advances in the control section D from
the left in FIG. 1, the self-inductances of loop coils .lambda. 10,
.lambda. 11 and .lambda. 12 are changed with advance of the
airplane and based on these changes, sensors S10, S11 and S12 put
out airplane detection signals sequentially and continuously. While
detection signals are put out from the sensors S10 through S12, it
is judged that the airplane is present in the control section D and
the signal lamp R is lighted to inhibit advance of a subsequent
airplane in the control section D. When the airplane in the control
section D has advanced into the forward control section completely,
a non-detection output is generated from the sensors in the control
section D, and when an admission signal is generated from the
forward control section, the signal lamp G is lighted to allow
advance of a subsequent airplane into the control section D.
Each of the above-mentioned sensors Si, signal processing unit 2
and switch circuits 6 and 7 has a fail-safe structure. Specific
circuit structure of these members will now be described.
Each of sensor Si is constructed so that it generates a
non-detection output of a high level (H level ) only when the loop
coil .lambda.i and the sensors Si are normal and an airplane is not
present in the loop coil .lambda.i and the sensor Si generates a
detection output of a low level (L level) when the loop coil or the
sensor gets out of order or an airplane is present in the loop
coil.
As shown in FIG. 2, the circuit for the sensor Si comprises a
high-frequency signal generator 12 driven by a power supplied from
a constant voltage power source circuit 11 to feed a high-frequency
current to the loop coil .lambda. i of the taxiway 1, a bridge
circuit 13 constructed by resistors Ra, Rb and Rc, the loop coil
.lambda. i in the state substantially resonating with the output
frequency of the high-frequency signal generator 12 and a capacitor
Cr, an alternating current amplifier 14 for amplifying an
unequilibriated voltage output of the bridge circuit 13, a
wave-detecting circuit 15 for detecting an envelope of an
alternating current output signal of the alternating current
amplifier 14, a window comparator 16 generating an oscillating
output when the output e2 of the wave-detecting circuit 15 is at a
level within a specific range (V1<e2<V2 in FIG. 3 ) and a
rectifying circuit 17 for rectifying the oscillating output of the
window comparator 16.
When an airplane is not present in the loop coil (i in the state
where a high-frequency electric current is supplied to the loop
coil (i from the high-frequency signal generator 12, as shown in
FIG. 3, the level of an output el obtained by amplifying the
unequilibriated output of the bridge circuit 13 by the alternating
current amplifier 14 is ell, and the level of an output e2 of the
wave-detecting circuit 15 of the subsequent stage is e21.
In contrast, when an airplane is present on the loop coil
.lambda.i, the unequilibriated output of the bridge circuit 13 is
increased by the change of the self-inductance of the loop coil
.lambda. i and the output level el of the alternating current
amplifier 14 is increased to e12, and also the output e2 of the
wave-detecting circuit 15 is increased to e22. For example, in case
of a loop coil of 30 m.times.40 m, the amplitude of this change,
that is, the induction change ratio, is about 0.8 % at largest for
an airplane (FIG. 4(A)) (Boeing 747) and about 0.3 % at largest for
an automobile (FIG. 4(B)) (towing car). as shown in FIG. 4.
The window comparator 16 is constructed so that the normal level
e21 of the output e2 of the wave-detecting circuit 15 in the
absence of an airplane is within the window and the output level
e22 in the presence of an airplane is outside the window.
Accordingly, when an airplane is not present, oscillation is caused
and the rectified output e3 of the rectifying circuit 17 becomes a
non-detection output of a high voltage (e3=logical value 1)
indicating the absence of an airplane, and when an airplane is
present, the oscillation is stopped and the rectified output e3
becomes an airplane-detecting output of a low voltage (e3=logical
value 0). If the low-voltage output obtained by stopping the
oscillation is thus adopted as the airplane-detecting output
inhibiting movement of a subsequent airplane, the
airplane-detecting output is made equal to the output at time of a
failure such as a circuit failure where no oscillation is caused.
Accordingly, the movement of a subsequent airplane is inhibited at
the time of a failure to secure safetY. and fail-safe control
becomes possible.
The logical product computing oscillation circuit which is the
basic circuit constituting the above-mentioned window comparator
will now be described with reference to FIG. 5.
This circuit comprises a feedback oscillating portion including two
NPN transistors Q1 and Q3, one PNP transistor Q2 and eight
resistors R1 through R8, and an amplifying portion including a
diode D1, an NPN transistor Q4 and four resistors R9 through R12
(see U.S. Pat. application Ser. No. 725,571 and Japanese Utility
Model Application No.59556/84).
The operation of this circuit is as follows.
When an input signal is not applied to input terminals I1 and I2,
the transistor Q1 is in the off-state and the transistors Q2 and Q3
are in the on-state, and no oscillating output is produced from an
output terminal f. If an input signal of a predetermined level
higher than a power source voltage Es is applied to the input
terminals I1 and I2 in this state, on-off changeover is repeated in
the transistors Q1 through Q3 in a manner as described below to
produce an oscillating output on the output terminal f. Namely,
through the operation of Q2 off.fwdarw.Q3 off.fwdarw.Q1
on.fwdarw.Q2 on .fwdarw.Q3 on.fwdarw.Q1 off ..., the oscillating
output on the collector side of the transistor Q3 is put in the
amplifying transistor Q4 through the diode D1 to produce an
oscillating output from the output terminal f.
The input signal conditions for generating an oscillating output
are substantially represented by the following formulae.
##EQU1##
wherein VI1 and VI2 respectively stand for input voltages of the
input terminals I1 and I2.
Accordingly, this circuit is an AND gate which oscillates only when
an input of a predetermined level higher than the power source
voltage Es is applied to the input terminals I1 and I2. If the
input terminals I1 and I2 are made common as indicated by a dot
line in FIG. 5, oscillation is caused at a logical product of both
the input voltages VIl and VI2, the conditions for the oscillation
input voltage VI (=VIl=VI2) are expressed by the following formula:
##EQU2##
As is seen from the foregoing illustration, if both the input
terminals I1 and I2 are made common, the logical product computing
oscillation circuit shown in FIG. 5 becomes a window comparator as
shown in FIG. 2, and an oscillating output is generated only when
the input signal level is within the range defined by the formula
(3). Incidentally, the input voltage range (window) defined by the
formula (3) can be changed according to values of the resistors
constituting the circuit.
Since the above-mentioned circuit does not generate an oscillating
output at the time of a failure, the circuit has such a
characteristic that an output signal is not erroneously generated
in the absence of the input signal, that is, a fail-safe
characteristic.
The rectifying circuit 17 shown in FIG. 2 is a voltage-multiplying
rectifier clamped at the power source voltage Es by a diode D2
shown in FIG. 6, and terminals 13 and 14 are connected to the power
source line Es and output terminal f shown in FIG. 5, respectively.
Only when the window comparator 16 oscillates, the level of the
rectified output e3 becomes higher than the power source voltage
Es, and when the window comparator 16 does not oscillate or the
rectifying circuit 17 gets out of order, a rectified output of a
level higher than the power source voltage Es is not produced.
If the circuit system is set so that the normal output e21 (the
absence of an airplane) of the wave-detecting circuit 15 is
included within the range defined by the formula (3) and the output
e22 in the presence of an airplane is outside this range,. output
characteristics as shown in FIG. 3 are given to the sensor Si. The
window comparator 16 and rectifying circuit 17 have the
above-mentioned fail-safe characteristics and the high-frequency
signal generator 12, alternating current amplifier 14 and
wave-detecting circuit 15 can be realized by using known fail-safe
structures in which no output is generated at the time of a
trouble. Moreover, if a failure such as breaking or formation of a
short circuit is caused in the resistors Ra, Rb and Rc, capacitor
CR and loop coil .lambda. i constituting the bridge circuit 13, the
unequilibriated output of this circuit is drastically increased and
the level of the output e2 of the wave-detecting circuit 15 is
outside the window of the window comparator 16. Accordingly, the
sensor Si having the structure shown in FIG. 2 has fail-safe
characteristics.
The structure of the signal processing unit will now be
described.
The direction- and object-discriminating circuit 3 for
discriminating the direction of an airplane and a moving object
(airplane or automobile) comprises, as shown in FIG. 7, first
through third AND gates A1, A2 and A3 constructed by NOT computing
circuits 21 and 22 by the above-mentioned window comparator and the
logical product computing oscillation circuit shown in FIG. 5,
respectively, rectifying circuits 23 through 27 having a structure
as shown in FIG. 6, a first self-retention circuit for feeding back
a rectified output of the first AND gate Al through a feedback
resistor R21 to the input terminal in which the output of the
sensor S10 corresponding to the loop coil (10 located on the inlet
side of the control section of the first AND gate Al, in which the
outputs of the sensors S10 and S11 connected to adjacent loop coils
.lambda. 10 and .lambda. 11 are put, and a second self-retention
circuit for feeding back a rectified output of the third AND gate
A3 through a feedback resistor R22 to the input terminal in which
an output of the second AND gate A2 is put.
The output Si (the rectified output e3 of the rectifying circuit
17) of the sensor Si put in the NOT computing circuits 21 and 22 is
an output of a negative signal (denial mode for detection) which is
at an H level on non-detection of an airplane and at an L level on
detection of an airplane. Accordingly, the output signal of the
sensor Si is designated as Si, and Si is equal to 0 when an
airplane is detected and Si is equal to 1 when an airplane is not
detected.
FIG. 7 illustrates the case where, supposing that an airplane moves
in the direction of from the loop coil (10 to the loop coil
.lambda. 11, the movement of an airplane is detected by output
signals S10 and S11 of the sensors S10 and S11.
This operation will now be described with reference to a time
chart.
The section for detection of an object by each of the loop coils
.lambda. 10 and .lambda. 11 is the sum (n+m) of a detection
effective section n (n<a) of the loop coil .lambda. 10
determined by a threshold value (detection level) set by the sensor
S10 and the length m of the floor face of an airplane effective for
detection. Since the interval between the loop coils .lambda.10 and
.lambda.11 is much smaller than the length of an airplane, the
detection outputs S10 and S11 by the loop coils .lambda.10 and
.lambda.11 are generated in the partially overlapped state as shown
in FIG. 8. Incidentally, in FIG. 8, output signals S10 and S11 are
NOT signals to the output signals S10 and S11.
The detection outputs S10 and S11 of the sensors S10 and S11 are
put in the AND gate Al through the NOT computing circuits 21 and
22. If the movement of an airplane is detected by the sensor S10,
the detection output S10 becomes "0" and the input signal S10 of
the first AND gate Al becomes "1". If the airplane-detecting output
(S11=0) is generated from the subsequent sensor in this state, the
other input signal S11 of the first AND gate Al becomes "1", and
the first AND gate Al oscillates. When a rectified output Sa from
the rectifying circuit 23 is applied to one input terminal of the
second AND gate A2, the input signal S11 of the first AND gate Al
is self-retained through the resistor R21 by the output of the
rectifying circuit 24 while the airplane is detected.
The second AND gate A2 oscillates when the airplane-detecting
signal (S10=0) of the sensor S10 disappears, and the second AND
gate A2 generates a direction-detecting output-generating output
Sb' as a rectified output of the rectifying circuit 25. This output
Sb' is put in the subsequent third AND gate A3 and is self-retained
through the resistor R22 by a rectified output of the rectifying
circuit 26 on extinction of the detection output of the sensor S11
(S11=1), and this output Sb' is kept generated while the
non-detection output (S11=1) of the sensor S11 is generated from
the rectifying circuit 27 of the third AND gate A3, whereby the
output Sb' is put out from the direction- and object-discriminating
circuit 3 as a direction detection output Sb indicating that the
airplane moves to the loop coils 11 from the loop coil
.lambda.10.
In the circuit shown in FIG. 7, when an airplane moves in the
reverse direction and the detection output signals are put out in
order of S11.fwdarw.S10, the first AND gate Al is not
self-retained, and when the output of the first AND gate Al
disappears, since the sensor S10 still generates the detection
output (S10=0), the direction detection output-generating output
Sb' is not generated from the second AND gate A2 and the
direction-detecting output Sb is not generated from the third AND
gate A3 (Sb=0) Furthermore, any of the NOT computing circuit 21 and
22, first through third AND gates Al through A3 and rectifying
circuits 23 through 27 does not generate an output when a failure
occurs. When failure is caused in the feedback resistors R21 and
R22, the self-retention is not effected, and therefore, a
continuous direction detection output is not produced.
Accordingly, this direction- and object discriminating circuit 3
has such a fail-safe structure that a detection output is
erroneously generated.
In case of an automobile which is shorter than the coil side a of
the loop coil .lambda. i, a detection signal is generated only in
the vicinity of the side of the loop coil, and if the interval
between adjacent loop coils is longer than the automobile, the
detection outputs S10 and S11 from the sensors S10 and S11 are not
produced in the overlapped state and if the adjacent loops are
located in the same place, the outputs simultaneously disappear.
Accordingly, any direction-detection output is not generated. Thus,
the loop coils respond only to an airplane but do not respond to an
automobile, and therefore, discrimination is possible between an
airplane and an automobile.
The display-instructing circuit 4 for generating a signal of
admission of advance in the control section and a signal of
inhibition of advance will now be described with reference to FIG.
9.
If an accident takes place on the taxiway 1, it is necessary that
use of the entire taxiway 1 should be inhibited or an airplane
should be guided by instructions of an air traffic controller
(manual operation). In view of this fact, the display-instructing
circuit 4 shown in FIG. 9 is provided with a manual mechanism.
A changeover switch SW1 of a manual operation device 5 is normally
connected to a contact C1 to give admission of advance on the
taxiway 1, and when an accident occurs, the switch SW1 is connected
to a contact C2 to cancel admission of advance and give an
inhibition signal for inhibiting advance in all of control sections
or specific control sections, and this changeover switch S1 acts as
a cancel switch for cancelling all of the operations of switches
SW2 through SW4 described hereinafter. The switch SW2 is a
direction-setting switch for setting the advance direction of an
airplane by an air traffic official. The switch SW3 is a changeover
switch for selecting automatic control (contact C3) or manual
control (contact C4)for the guidance of an airplane when admission
of advance is given by the changeover switch SW1. The switch SW4 is
a manual advance-admitting instruction switch for giving an
advance-admitting instruction signal appropriately by the air
traffic controller when the manual control is selected by the
switch SW3.
In the display-instructing circuit 4, when admission of advance in
the taxiway is given and the direction instructed by the air
traffic controller is in agreement with the direction detection
signal Sb from the direction- and object-discriminating circuit 3,
an output is generated from a fourth AND gate A4 through a
rectifying circuit 31. If the switch SW3 is connected to the
contact C3 at this point, the automatic operation is selected and
an advance-admitting signal is automatically put in a fifth AND
gate A5, and if the switch SW3 is connected to the contact C4, the
manual operation is selected and if the switch SW4 is turned on at
the will of the air traffic controller, an advance-admitting signal
is put in the fifth AND gate A5, whereby an admission signal fl to
a control section (control section D shown in FIG. 1) in the rear
of the control section through which an airplane is now advancing
(the control section on the forward side of the control section D
shown in FIG. 1) is generated from the fifth AND gate A5 through a
rectifying circuit 32 and this signal is applied to one input
terminal of an AND gate A8 as advance admission-instructing means.
Namely, advance-admitting signal-generating means is constructed by
the fourth and fifth AND gates A4 and A5 and the rectifying
circuits 31 and 32.
If an airplane-detecting signal is not generated from any of the
sensors S10, S11 and S12 corresponding to the loop coils .lambda.
10, .lambda. 11 and .lambda. 12 in the control section D (S10=S11
=S12=0), an output f2 of an AND gate A6 is converted to a
non-inhibition signal of a high voltage through a rectifying
circuit 33 by the output generated through a rectifying circuit 34
of an AND gate A7 and this non-inhibition signal is applied to the
other input terminal of the AND gate A8, whereby an
advance-admitting display-instructing signal f3 of a high voltage
is generated from the AND gate A8 to light the signal lamp G and
admit advance in the control section D.
Namely, the signal f3 for instructing display of admission of
advance in the control section D is generated only when the
direction of advance is in agreement with the direction instructed
by the air traffic controller to generate the direction-detection
signal in the control section on the forward side of the control
section D and an airplane is not present in the control section
D.
Incidentally, if an airplane is present in the control section D, a
detection output (S10, S11, or S12=0) is generated from any of the
sensors S10, S11 and S12, and therefore, the output f2 from the AND
gate A6 becomes an advance-inhibiting signal of a low level and the
advance-admitting display-instructing signal f3 of the AND gate A6
is not generated, and simultaneously, the advance-inhibiting signal
lamp R is lighted to inhibit advance in the control section D. A
sixth AND gate is constructed by the AND gates A6 and A7, and the
advance-inhibiting signal-generating means is constructed by the
AND gates A6 and A7 and, the rectifying circuits 33 and 34.
When an accident occurs on the taxiway 1, the switch Sw1 is changed
over to the contact C2 to generate an advance-inhibiting signal for
all of the control sections or specific control sections. Since any
of the AND gates A4 through A8 does not generate an output at the
time of a trouble or accident, an advance-admitting signal of a
high voltage is not produced at all and a fail-safe effect is
attained. Incidentally, in the case where bidirectional advance of
airplanes is carried out, another circuit of a similar structure is
disposed for the other advance direction.
When an airplane does not pass, as just after changeover of the
direction of guidance of an airplane, no direction detection signal
is generated. However, as is obvious to those skilled in the art, a
signal f3 for instructing display of admission of advance in the
control section D can be generated by forming wired OR connection
between a non-inhibition signal f4 generated from the non-detection
signals of the respective sensors of said control section and an
admission signal fl generated by a manual switch SW5 indicated by a
dot line in the drawings.
FIGS. 10 and 12 illustrate switch circuits 6 and 7 of the admission
signal lamp G and inhibition signal lamp R in which the
advance-admitting display-instructing signal f3 and
advance-inhibiting signal f2 from the display-instructing circuit 4
are put, respectively.
The admission signal lamp circuit 6 will now be described.
In the admission signal lamp switch circuit 6, a solid state relay
(hereinafter referred to as "SSR") is used as the switch element,
and at the time of a failure, SSR shows both the switch states of
breaking (OFF) and short circuit (ON) seen from the output side.
Accordingly, there is a risk of displaying an admission signal or
an inhibition signal according to the kind of the failure, and
especially, display of the admission signal results in collision of
airplanes. Accordingly, erroneous display of the admission signal
at the time of a failure should be avoided.
Accordingly, in the admission signal lamp switch 6, a watch circuit
50 surrounded by a chain line in FIG. 10 is arranged to inspect
whether or not SSR is normally operated and cut off the power
source of the signal lamp G at the time of a failure.
Referring to FIG. 10, a rectifying circuit 41 rectifies the
advance-admitting display-instructing signal f3 from the AND gate
A8 shown in FIG. 9 and supplied the rectified output to SSR
performing switching of the signal lamp G. In general, SSR is
turned off when an input signal of a high voltage is applied, and
SSR is turned on when an input signal of a low voltage is applied.
Incidentally, a constant current power source 42 is generally used
as the power source for the signal lamp G.
The watch circuit 50 for inspecting the operation state of SSR
comprises a rectifying circuit 51 for generating a rectified output
formed by overlapping a direct current voltage V1 on the
advance-admitting display-instructing si f3, a rectifying circuit
53 for generating a rectified output formed by overlapping the
direct current voltage V1 on the output of a current sensor 52 as
the current detecting means for detecting the presence or absence
of the output current of SSR, AND gates 54 and 55 having a window
comparator function of comparing logically the values of the
outputs of both the rectifying circuits 51 and 53, which oscillate
when the input-output relation is normal, a D/A converter 56
constituted by the AND gate similar to the one shown in FIG. 5 for
converting a wired OR output (digital) of both the AND gates 54 and
55 to an analogue output, an alternating current amplifier 57, and
a rectifying circuit 58 for rectifying the alternating current
amplified output, and the watch circuit 50 controls the driving of
an electromagnetic relay 59 as the current cut-off means for
performing the on-off control of the constant current power source
42 and signal lamp G by the rectified outputs.
The operation of the watch circuit 50 will now be described.
The relation between the input signal (advance-admitting
display-instructing signal f3) and the output signal (output
current of SSR) in the normal state where the electromagnetic relay
59 is connected to a contact r1 is such that when the input is "1",
the output is "0" and when the input is "0", the output is "1".
Namely, when the input is "1", the contact of SSR is turned off to
light the signal lamp G, and when the input is "0", the contact of
SSR is turned on to put out the signal lamp G by formation of a
short circuit.
When the input signal f3 from the AND gate A8 is supplied, the
output overlapped with the voltage V1 from the rectifying circuit
51 is applied to the input terminal Il of the AND gate 54 and the
input terminal I2 of the AND gate 55. Furthermore, the rectified
output formed by overlapping the voltage V1 on the output of the
electric current sensor 52 is applied to the other input terminals
I2 and I1 of the AND gates 54 and 55. The power source voltage V2
of both the AND gates 54 and 55 is set at a level lower than the
overlapped voltage V1 in the rectifying circuits 51 and 53.
The AND gate 54 oscillates when the input signal is "1" 55
oscillates when the input signal is "0" and the output of the
current sensor is "1". The AND gates 54 and 55 does not generate an
oscillation output in any of the other input-output relations.
Accordingly, supposing that the voltages attained when the input
signal and the output signal of the current sensor are logical
value 1 (high voltage) are Vf and Vs, respectively, the oscillation
condition for the AND gate 54 on the side of the input terminal Il
is expressed by the following formula: ##EQU3## and the oscillation
condition for the AND gate 54 on the side of the input terminal I2
is represented by the following formula: ##EQU4##
The oscillation condition for the AND gate 55 on the side of the
input terminal Il is represented by the following formula: ##EQU5##
and the oscillation condition for the AND gate 55 on the side of
the input terminal I2 is represented by the following formula:
##EQU6##
In short, the logical sum (wired OR) output of the AND gates 54 and
55 becomes logical value "1" only when the input-output relation is
normal.
Accordingly, the D/A converter 56 generates an oscillating output
only when the input-output relation is normal, and this output is
amplified by the alternating current amplifier 57 and rectified by
the rectifying circuit 58. By the rectified output, the
electromagnetic relay 59 is excited to close the contact r1.
Accordingly, only in the normal state, the signal lamp G is put on
and off by the admission signal lamp switch circuit according to
the on-off state of SSR. At the time of a failure or accident, the
electromagnetic relay 59 is not excited and the signal lamp G is
not lighted. Since the watch circuit 50 has a fail-safe structure
and does not generate an output at the time of a failure, erroneous
lighting of the admission signal lamp G by a failure in the watch
circuit 50 is prevented.
Incidentally, the watch circuit 50 detects occurrence of a failure
when the input signal is "0" and the sensor output signal is "0",
but if the input signal is then changed to "1" while the sensor
output signal is maintained at "0", the input-output relation
becomes equal to the normal input-output relation and judgement of
the failure is cancelled.
In order to prevent occurrence of this phenomenon, there may be
adopted, for example, a structure in which, as shown in FIG. 11, a
presettable self-retention circuit is disposed as the D/A converter
56 (in this case, the D/A converter acts as an AND gate), and if a
normal signal is generated by the on-operation of a preset switch
60 the normal signal is self-retained and stored by a feedback
resistor R even after the off-operation of the switch 60 and if the
oscillaton of the D/A converter 56 is stopped at the time of a
failure and the self-retention is reset, the normal signal is not
put out unless the preset switch 60 is turned on again.
An inhibition signal lamp switch circuit (signal lamp switch
circuit 7 in FIG. 1) shown in FIG. 12 is provided with SSR 61 as a
switch element which is turned on when the output of the AND gate
A6 shown in FIG. 9 is at the H level and is turned off when the
output of the AND gate A6 is at the L level, and the inhibition
signal lamp R is connected to this switch circuit in parallel to
SSR 61. A constant current power source 42 resembling the power
source circuit for the admission signal lamp G is used as the power
source. The operation of this circuit will now be described.
If, for example a detection signal (L level) is generated from any
one of the sensors S10, S11 and S12 in the control section D, the
output of the AND gate is turned to an L level, whereby SSR 61 is
turned off and the inhibition signal lamp R is lighted. If any of
the sensors S10, S11 and S12 does not generate a detection signal
and an airplane is not present in the control section D, the
non-inhibition signal f2 of an H level is generated from the AND
gate A6 and SSR 61 is turned on, whereby the inhibition signal lamp
R is put off by formation of a short circuit.
Special cares should be taken in the guidance control for guiding
airplanes safely.
Since the rear end portion of an airplane is located at a high
position, even if the rear end portion does not completely separate
from the loop coil .lambda. i but is left in the loop coil
.lambda.i region, the change of the self-inductance is small and
the sensor output becomes a non-detection output. The first concern
is to cope with this phenomenon.
For example, referring to FIG. 1, if an airplane advances in the
control section D and passes through the loop coils .lambda. 10 and
.lambda.11, the advance-admitting signal fl to the rear control
section is generated at the time point when the non-detection
signal (S11=1) of the sensor S11 is generated. However, as pointed
out hereinbefore, there is a possibility that the rear end portion
of the airplane is still present in the loop coil (11. An AND gate
A9 for computing the logical product of the rectified output of the
AND gate A5 and the output S9 of the sensor S9 is disposed
precedently to the AND gate A8, as shown in FIG. 13, so that while
admitting that an airplane is apparently absent on the loop coil
.lambda.9 in the rear of the loop coil (11, the advance-admitting
signal fl is produced only when the non-detection output (S9=1) is
generated in the sensor S9 of the loop coil .lambda.9, and the
output signal f1' of the AND gate 9 is adopted as the
advance-admitting signal to increase the safety.
Another concern is for guidance control at the crossing point of
taxiways.
FIGS. 14(A), 14(B) and 14(C) show different running patterns at the
crossing point P. Namely, FIG. 14(A) shows the case where the
direction of an airplane in a taxiway 1A is set so that the
airplane joins with a stream of airplanes running from a taxiway 1B
to a taxiway 1C or from the taxiway 1C to the taxiway 1B, FIG.
14(B) shows the case where a direction-admitting signal is
necessary for running of an airplane in a taxiway 1A where advance
in a taxiway 1B or 1C from the taxiway 1A and advance in the
taxiway 1A from the taxiway 1B or 1C are carried out, and FIG.
14(C) shows the case where two taxiways 1A and 1B cross each
other.
In the case where an airplane advances in control section D1, D2,
D3 and D4 extending from the crossing point, it is required that an
airplane should not be present on the crossing point P and
furthermore, even a wing of the plane should not be present on the
crossing point P. Accordingly, in this case, the condition for
admission of advance is that an airplane should not be present on
the crossing point P and in any of control sections D1, D2, D3 and
D4 adjacent to the crossing point P.
Therefore, a logical product output of outputs P, D1, D2, D3 and D4
of sensors at the crossing point P and the control sections D1
through D4 (P=D1=D2=D3=D4=0 at the time of detection of an
airplane) is put in the AND gate A9 instead of S9 shown in FIG. 13
in the control sections adjacent to the crossing point P.
When a failure is caused in sensors or loop coils, the signals P,
D1, D2, D3 and D4 are erroneously set at 0, and therefore, an
advance admission signal is not generated and a fail-safe structure
is realized.
If the guidance control system is constructed so that an airplane
is continuously detected by loop coils (i arranged continuously in
a taxiway 1 as described hereinbefore, the presence or absence of
an airplane in the control sections can always be detected without
using a memory, and safe guidance of airplanes can be realized.
Since the sensor output patterns of an airplane and an automobile
are made different from each other according to the shape and
arrangement structure of the loop coils, an erroneous operation
owing to passage of an automobile can be prevented, and since a low
level (including an output of zero) signal is used as the airplane
detection signal instead of the customarily adopted detection
signal and this signal errs to an inhibition signal on occurrence
of a failure in the control system, a fail-safe structure is
realized and guidance of airplanes can be controlled with a very
high safety.
An embodiment in which advance-admitting and advance-inhibiting
signals are redundantly obtained will now be described.
In the ground guidance system of the present invention, since the
sensor Si of the loop coil (i detects a small change of a signal,
the reliability is generally low. Accordingly, the reliability of
this guidance control system depends greatly on the reliability of
the sensor Si including the loop coil .lambda.i. The redundant
control for increasing the reliability of the sensor Si will now be
described.
The redundant control of generation of advance-admitting signals is
first described.
FIG. 15 illustrates a direction- and object-discriminating
signal-generating circuit for redundantly obtaining a direction-
and object-discriminating signal for obtaining an admission of
advance by output signals S10, S11 and S12 from the sensors S10
through S12 in the control section D shown in FIG. 1.
In FIG. 15, direction- and object-discriminating circuits 71, 72
and 73 have a structure shown in FIG. 7, and the outputs S10 and
S11, the outputs S11 and S12, and the output S12 and the sensor
output S13 of the subsequent control section are used as input
signals of the circuits 71, 72 and 73, respectively. As an airplane
runs in the control section D, the direction- and
object-discriminating circuits 71, 72 and 73 sequentially generate
direction-object discrimination output signals. The direction- and
object-discriminating circuits 71, 72 and 73 are constructed so
that these direction-object discrimination signals are transmitted
to the circuit of the subsequent stage for the first time when at
least the sensor located ahead, in the direction of advance, of the
sensors generating input signals for the direction- and
object-discriminating circuits 71, 72 and 73 generates a
non-detection output. Namely, the output signal of the direction-
and object-discriminating circuit 71 is transmitted to the circuit
of the subsequent stage through an AND gate A21 and a rectifying
circuit 74 when the output S9 of the sensor S9 corresponding to the
loop coil .lambda. 9 is changed to a non-detection output (S9=1),
and the output signal of the direction- and object-discriminating
circuit 72 is transmitted to the circuit of the subsequent stage
through an AND gate A22 and a rectifying circuit 75 when the output
S9 or S10 of one of the sensors S9 and S10 is changed to a
non-detection signal (S9 or S10=1). Furthermore, the output signal
of the direction- and object-discriminating circuit 73 is
transmitted to the circuit of the subsequent stage through an AND
gate A23 and a rectifying circuit 76 when the output S9, S10 or S11
of one of the sensors S9, S10 and S11 is changed to a non-detection
output (S9, S10 or S11=1). These outputs are converted to one
direction-object discrimination signal x by wired OR.
Accordingly, the direction-object discrimination signal x is
generated when it passes through the sensor S12 in the case where
the sensor S9 gets out of order, when it passes through the sensor
S12 in the case where the sensor S10 gets out of order, when it
passes through the sensor S13 in the case where the sensor S11 gets
out of order and when it has already passed through the sensor S11
by the direction- and object-discriminating circuit 71 in the case
where the sensor S12 gets out of order.
Namely, in the direction- and object-discriminating
signal-generating circuit shown in FIG. 15, even if any one of the
sensors S9, S10, S11 and S12 gets out of order, the
direction-object discrimination signal x can be generated by other
normal sensors. Furthermore, the redundant control can be performed
in such a fail-safe manner that any direction-object discrimination
signal is not generated before the time point of generation of the
direction-object discrimination signal in the normal state.
Accordingly, when the direction-object discrimination signal x is
generated, generation of an advance-admitting signal to the control
section in the rear of the control section D in the direction of
advance of an airplane becomes possible, and therefore, redundant
fail-safe control of generation of advance-admitting signals
becomes possible.
Then, the redundant control of generation of advance-inhibiting
signals is described.
In the control circuit shown in FIG. 9, in the case where any one
of the sensors in the control section D gets out of order, an
advance-inhibiting signal is generated (the non-inhibition signal
f2 disappears). However, in view of utilization of the taxiway 1, a
certain control function is necessary in a control section provided
with a plurality of sensors even if any one of these sensors gets
out of order.
FIG. 16 shows an advance-inhibiting signal-generating circuit for
redundantly obtaining a signal for inhibiting advance in the
control section D when one of a plurality of sensors gets out of
order.
Referring to FIG. 16, AND gates A31, A32 and A33 receive output
signals S10, S11 and S12 of sensors S10, S11 and S12 as one input
signal and wired OR outputs of S9 and S10, S10 and S11, and S11 and
S12 as the other input signal. Capacitors C31, C32 and C33 and
diodes D31, D32 and D33 are disposed to preset rising components of
the output signals S10, S11 and S12 of the AND gates A31, A32 and
A33 (at the point of termination of detection of an airplane by
each sensor), and they are clamped at the power source voltage E by
the diodes D31, D32 and D33. The AND gates A31, A32 and A33 are
provided with self-retention circuits in which outputs of the AND
gates A31, A32 and A33 are fed back to one input sides through
feedback resistors R31, R32 and R33 and are self-retained. An AND
gate A34 is disposed to compute the logical product of the outputs
of the AND gates A31 and A32, and an AND gate 35 is disposed to
compute the logical product computation output of the AND gate A34
and the output of the AND gate A33. Rectifying circuits 81 through
88 are disposed to rectify oscillating outputs of the AND gates A31
through A35.
The advance-admitting signal f given from the control section
ahead, in the direction of advance of an airplane, of the control
section D is applied to input terminals on the preset sides of the
AND gates A31, A32 and A33 through a buffer circuit 89 and
rectifying circuits 90, 91 and 92 constituted by the AND gates
circuits, and the AND gates A31, A32 and A33 are preset also by
this advance-admitting signal f.
The operation will now be described with reference to the time
chart of FIG. 17.
Of sensors S9 through S13, every two adjacent sensors put out
detection signals (Si=0) in the partially overlapped state with
advance of an airplane, as shown in FIG. 17. When an airplane
advances in the control section D and the sensor S10 detects this
advance, since the sensor S9 still puts out a detection signal at
this point the wired OR output of S9 and S10 is at an L level and
the AND gate A31 is reset, with the result that the output Ul of
the AND gate A31 disappears. Simultaneously, the outputs of the AND
gates A34 and A35 disappear, and an advance-inhibiting signal y is
put out.
Then, as the airplane runs, the output S10 of the sensor S10 is
changed to a non-detection signal from the detection signal, and by
the rising component of this signal, the AND gate A31 is present,
and the level of the output Ul of the AND gate A31 is increased to
an H level and this signal is put in the AND gate A34. The same
patterns are taken with respect to outputs U2 and U3 of the AND
gates A32 and A33.
Since the reset states of the AND gates A31, A32 and A33 are
partially overlapped on one another, the advance-inhibiting signal
y is kept generated during the period of from the point of
resetting of the AND gate A31 to the point of presetting of the AND
gate A33, as shown in FIG. 17, that is, during the period from the
point of detection of the airplane by loop coil .lambda. 10 to the
point of non-detection of the airplane by the loop coil .lambda.
12.
In the advance-inhibiting signal-generating circuit which is
operated in the above-mentioned manner, for example, if the loop
coil .lambda.10 or the sensor S10 gets out of order, since S10 is 0
the output of the AND gate A31 disappears at the point of S9=0, and
the advance-inhibiting signal y is generated. The rising component
of S10 is not generated and the AND gate A31 is kept reset, but
when the advance-admitting signal f is generated from the control
section ahead of the control section D, the AND gate A31 is preset
by this signal, and therefore, the advance inhibition range defined
by the AND gate A31 is from the point of generation of the
detection signal by the sensor S9 to the point of generation of the
advance-admitting signal f. Incidentally, in this case, the
operations of the AND gate A32 and A33 are the same as in the
normal state. Accordingly, when the loop coil .lambda. 10 or the
sensor S10 gets out of order, the range of generation of the
advance-inhibiting signal y in the control section D is the sum of
the normal range and the range from the point of generation of the
detection signal of the sensor S9.
When the loop coil .lambda. 11 or the sensor S11 gets out of order,
in the same manner as described above, the output U2 of the AND
gate A32 is reset at the point of generation of the detection
signal by the preceding sensor S10, and the advance-inhibiting
signal is generated by the AND gate A32 until the output U2 is
preset by the advance-admitting signal f. Also in this case, the
AND gates A31 and A33 are normally operated, and therefore, the
range of generation of the advance-inhibiting signal y is the same
as the normal. In case of the loop coil 12 or the sensor S12 gets
out of order, the range of generation of the advance-inhibiting
signal is the same as the normal generation range.
Namely, the advance-inhibiting signal-generating circuit shown in
FIG. 16 is constructed so that when one of the loop coils (i or the
sensors Si gets out of order, the advance-inhibiting signal
generation range is not made narrower than the normal
advance-inhibiting signal generation range, and fail-safe redundant
control can be performed without reduction of safety.
If the wired OR output of the output S10 of the sensor S10 and the
output S11 of the subsequent sensor S11 is used instead of the
output S10 of the sensor S10 as the preset signal for the AND gate
A31 as indicated by a dot line in FIG. 16, when the loop coil (10
or the sensor S10 gets out of order, the output U1 of the AND gate
A31 rises at the point of generation of the non-detection signal by
the sensor S11 and the advance-inhibiting range defined by the AND
gate A31 can be extended to the point of termination of the
detection by the sensor S11. Although the AND gate using the output
of the sensor, which gets out of order, as the preset signal is
kept in the reset state if an advance-inhibiting signal is once
generated, by adopting a structure in which this AND gate can be
preset even by the advance-admitting signal, it becomes possible to
display admission of advance in the control section D for a
subsequent airplane, and delay of guidance and control of airplanes
is not caused.
As is apparent from the foregoing description, according to the
present invention, since a plurality of loop coils are arranged in
each control section of a taxiway and airplanes running on the
taxiway are detected perpetually and continuously, the utilization
efficiency of the taxiway can be increased. Furthermore, when a
failure occurs in the system, outputs disappear without fail and a
state similar to the state where an airplane is detected is
produced to stop running of a subsequent airplane. Therefore, a
fail-safe effect can be attained assuredly.
Industrial Applicability
As is apparent from the foregoing description, the ground guidance
system for airplanes according to the present invention is
effectively applied to an airport where airplanes frequently take
off and land, and the utilization efficiency of the airport can be
increased.
* * * * *